Formal “When”: 際・折・時 in Japanese

In Brief

Use 際（さい） for a formal, practical “when” or “on the occasion of,” especially in notices, instructions, and business language. Use 折（おり） for a more literary or letter-like “when the opportunity arises.” 時（とき） remains the broad, neutral choice and appears in useful advanced patterns such as 困った時は and いざという時.

Overview

At A2, とき gives you a general way to connect an event or state with a time: 日本へ行くとき (“when going to Japan”), 暇なとき (“when free”), and 子供のとき (“when I was a child”). At B2, you begin choosing among expressions that package the same basic time relationship in different styles. This choice is about register (the level of formality and style appropriate to a situation), not simply politeness endings.

You will often meet 際 on websites, application forms, signs, product instructions, and in customer service. 折 is less common in ordinary conversation; it belongs especially to courteous letters, invitations, speeches, and carefully worded messages. 時 is much wider: it can be conversational or formal, and the particles and surrounding words determine whether it means “when,” “in case,” “at that point,” or “in a moment of need.”

English lets “when” cover all these situations, so translating word for word is unreliable. A useful question is not only “When does this happen?” but also “Am I describing an ordinary time, an official occasion, or a welcome opportunity?”

How It Works

The central contrast

Form	Core sense	Typical register and setting	Example frame
時（とき）	time; when	neutral and general; speech and writing	困った時は…
際（さい）	occasion; at the time of	formal, practical, official	ご利用の際は…
折（おり）	occasion; opportunity	refined, literary, often personal	お近くにお越しの折には…
機会（きかい）	opportunity, chance	neutral to formal; stresses the chance itself	この機会に…

These words are nouns (words naming a thing or idea), but a clause can modify them just as English modifies “time” in “the time when we met.” Japanese puts the modifying material before the noun.

Forming phrases with 際

The basic patterns are:

Modifier	Pattern	Example	Meaning
Verb, non-past plain form	Vる + 際（に／は）	申請する際に	when applying
Verb, past plain form	Vた + 際（に／は）	お会いした際に	when I met you
Noun	Nの + 際（に／は）	ご来店の際に	when visiting the store
な-adjective or adjectival expression	な + 際（に／は）	ご不明な際は	if anything is unclear

The plain form is the verb form used before items such as とき: for example, 利用する, 利用した, 利用しない. A polite sentence may still contain a plain-form verb inside this modifying clause: 変更する際は、事前にご連絡ください. Do not put ます directly before 際.

際に marks the occasion as a time within the sentence. 際は makes that occasion the topic (what the rest of the sentence is about) and often introduces an instruction or condition. Compare:

• 受付をした際に、番号札を受け取りました。 — I received a numbered ticket when I checked in.
• 受付をする際は、身分証をご提示ください。 — When checking in, please show identification.

The second sentence sounds like a general instruction. This is one reason 際は is so common in notices.

Forming phrases with 折

折 takes similar modifiers:

Pattern	Example	Natural interpretation
Vる + 折（に／は）	お越しになる折には	when you come / should you have occasion to come
Vた + 折（に）	お目にかかった折に	when I had the pleasure of meeting you
Nの + 折（に／は）	帰国の折には	upon your return to the country

The grammar resembles 際, but the feeling is different. 折 presents the event as a particular occasion, often one that offers a suitable opportunity. It frequently appears with gracious invitations and requests: その折には、ぜひお立ち寄りください (“When that occasion arises, please do stop by”).

Do not treat 折 as an all-purpose formal replacement for とき. A machine manual, emergency warning, or routine rule normally calls for 際 or 時, not the softer, more literary 折.

Advanced choices with 時

時 follows the familiar patterns Vる時, Vた時, い-adjective + 時, な-adjective + な時, and Nの時. At this level, pay attention to the viewpoint created by the verb form.

• 出かける時、電気を消しました。 — I turned off the lights when leaving. The leaving is viewed as not yet completed at the relevant moment.
• 帰った時、電気がついていました。 — When I returned, the lights were on. The return had been completed when the situation was observed.

This is a relationship between the event before 時 and the main event, not a simple English-style tense agreement rule. Context and the kind of verb matter, so avoid memorizing “る時 means future” and “た時 means past.” Both can occur in a sentence about the past.

Particles create several useful patterns:

Pattern	Function	Example
時に	at the time when; at a particular point	必要な時に使う
時は	when/in cases where; sets a condition or topic	困った時は相談する
時には	at times; sometimes	時には休むことも必要だ
その時（に）	then; at that moment	その時に決めます
その時点で	at that point/stage	その時点で受付を終了します
いざという時（に）	in an emergency or crucial moment	いざという時に備える
必要な時に	when needed	必要な時にご利用ください

Where 機会 fits

機会 does not merely locate an action in time. It names a chance or opportunity to do something. That is why この機会に申し上げたいことがあります means “I have something I would like to say on this occasion”: the speaker is using the present occasion as an opportunity.

Compare 日本へ行く際に友人に会います (“I will meet a friend when I go to Japan”) with 日本へ行く機会があれば友人に会いたいです (“If I get an opportunity to go to Japan, I would like to meet a friend”). The first assumes the trip as the occasion; the second focuses on whether the chance will arise.

Examples in Context

Japanese	English	Note
お越しの際は、ご連絡ください。	Please contact us when you come.	Formal request with noun + の際は
ご利用の際は、利用規約をご確認ください。	When using the service, please review the terms of use.	Typical notice or website wording
申請する際に、本人確認書類が必要です。	Identification is required when applying.	際に marks the application occasion
先日お会いした際には、貴重なお話をありがとうございました。	Thank you for the valuable conversation when we met the other day.	Refers politely to a completed meeting
万一事故が発生した際は、直ちに係員へお知らせください。	In the event of an accident, notify a staff member immediately.	Formal contingency instruction
ご不明な点がある際は、担当者までお問い合わせください。	If anything is unclear, please contact the person in charge.	Formal conditional use
帰国の折には、お立ち寄りください。	Please drop by when you return to the country.	Courteous invitation using 折
お近くにお越しの折には、ぜひお声がけください。	If you happen to be in the area, please do get in touch.	Warm, polished, and letter-like
以前京都を訪れた折に、この寺を知りました。	I learned about this temple when I visited Kyoto before.	Recollection in a literary style
困った時はいつでも相談してください。	Please talk to me whenever you are in trouble.	Neutral, supportive advice
出発する時、窓を閉めました。	I closed the windows when I was about to leave.	The departure was not yet complete
駅に着いた時、雨が降り始めました。	When I arrived at the station, it began to rain.	Arrival completed before the observation
その時点で提出されていない書類は受理できません。	Documents not submitted by that point cannot be accepted.	Precise procedural deadline
いざという時に備えて、水を保管しています。	We store water in preparation for an emergency.	Fixed expression for a crucial moment
この機会に申し上げたいことがあります。	I have something to say on this occasion.	The occasion is treated as an opportunity

Common Mistakes

Putting a polite verb directly before 際

• Wrong: お申し込みします際は、こちらをご確認ください。
• Right: お申し込みの際は、こちらをご確認ください。
• Also right: お申し込みになる際は、こちらをご確認ください。
• Why: The clause before 際 uses a plain form, not ます. With the noun お申し込み, use の.

Using 折 for a routine warning

• Awkward: 火災が発生した折は、非常口から避難してください。
• Natural: 火災が発生した際は、非常口から避難してください。
• Why: Emergency instructions need direct, practical wording. 折 suggests a noteworthy or welcome occasion and sounds mismatched here.

Replacing every とき with 際

• Overly formal: 子供の際、よく川で遊びました。
• Natural: 子供の時、よく川で遊びました。
• Why: An ordinary life stage normally takes 時. 際 is most natural for bounded situations, actions, procedures, or formal contingencies.

Treating る時 and た時 as future and past tense

• Misleading rule: 出る時 is future; 出た時 is past.
• Better contrast: 家を出る時、鍵をかけた / 家を出た時、雨に気づいた。
• Why: The form shows how the event is viewed relative to the main event: before completion versus after completion. The whole sentence can describe the past.

Confusing an occasion with an opportunity

• Different meaning: 会議の際に質問しました。 — I asked a question during/at the meeting.
• Different meaning: 質問する機会がありませんでした。 — I did not have an opportunity to ask a question.
• Why: 際 locates the action at an occasion; 機会 emphasizes whether a chance existed.

Usage Notes

際 is common in language addressed to the public because it is compact and impersonal. Phrases such as ご利用の際, お申し込みの際, and 緊急の際 let an organization state what should happen under a defined condition. In casual conversation, however, 使うとき or 申し込むとき will usually sound more relaxed and natural.

The formal effect often comes from the whole phrase, not from 際 alone. Honorific forms such as お越し, ご利用, and お申し込み commonly surround it. Honorific here means language that respectfully raises the person being addressed or their action. Nevertheless, 際 can occur without honorific vocabulary: 交換する際は、電源を切ってください is formal because of its instructional setting.

折 is alive in modern Japanese, but its range is narrower. It works well in greetings, correspondence, acknowledgements, and invitations where the writer looks back on or anticipates a meaningful occasion. Formula-like expressions include その折は (“on that occasion”) and その折には (“when that occasion arises”). In an everyday chat, they can sound ceremonious.

Writers may use kanji 時 or hiragana とき. Style guides and individual publications differ. Kanji often looks more concrete when referring to a particular time, while hiragana is common in grammatical or conditional uses, but actual practice is not completely uniform. Consistency with the document’s style matters more than inventing an absolute rule.

Beyond the Basics / Advanced Use

際に versus に際して

Nに際して and Vるに際して mean “on the occasion of” or “when undertaking.” They are more formal and ceremonial than ordinary 際に, and often introduce preparations, statements, or requirements connected with an important event.

• 開会に際して、一言ご挨拶申し上げます。 — On the opening of the event, I would like to say a few words.
• 契約を更新するに際して、条件を再確認しました。 — When renewing the contract, we reviewed the conditions.

The related にあたって often has a similar meaning and is common when beginning or facing an important undertaking: 新事業を始めるにあたって. These patterns are not interchangeable in every sentence, but both frame an event as significant rather than merely locating it in time.

際 as “boundary” or “edge” in compounds

Do not assume every 際 is read さい or means “occasion.” In words such as 国際（こくさい） it forms part of a compound, and in 窓際（まどぎわ） the reading ぎわ means “by/at the edge of.” The grammar pattern taught here is the independent noun 際（さい） after a modifier.

時 in conventional expressions

Several fixed expressions go beyond plain “when”:

• 時と場合による — it depends on the time and circumstances
• 時がたつ — time passes
• 時を置かず — without delay
• 時には — at times, sometimes
• いざという時 — a critical moment, especially an emergency

Also distinguish 時に（ときに）, “at the time,” from the formal conjunction 時に（ときに）, “by the way/now,” occasionally used to shift topic in speeches or writing. Context and punctuation usually make the latter clear; it is not the ordinary temporal pattern.

Negative and hypothetical situations

際 commonly appears in negative or hypothetical official conditions: ログインできない際は, 該当しない際は, 万一遅延が生じた際は. In many such cases, 場合（ばあい） is also possible and may be even clearer as “in the event/case that”: ログインできない場合は. 場合 classifies a case or condition; 際 presents it as the occasion on which an action is taken. Formal writing often chooses between them according to emphasis rather than a sharp difference in factual meaning.

Practice Tips

1. Rewrite by register. Take a neutral sentence such as 店に来る時、電話してください and make it suitable for a customer notice (ご来店の際は、ご連絡ください) and then for a gracious letter (お近くにお越しの折には、お声がけください). This trains meaning and tone together.
2. Collect complete frames, not isolated words. Save phrases such as ご利用の際は, その折には, 困った時は, and いざという時に. Notice what request or statement typically follows each frame.
3. Track event order with a timeline. For pairs such as 出る時 and 出た時, mark whether the action before 時 is incomplete or complete at the main event. This is more reliable than translating both as English “when.”

Related Concepts

• Prerequisite: とき (when) — the basic modifier patterns and event-order contrast that 際, 折, and advanced 時 expressions build on